POS0132 THE FIRST ALGORITHM TO INTEGRATE ULTRASONOGRAPHY IN THE DIAGNOSTIC PROCESS OF DIFFERENTIAL DIAGNOSIS OF INFLAMMATORY ARTHROPATHY IN CLINICAL PRACTICE: A STUDY FROM THE MSUS WORKING GROUP OF THE ITALIAN SOCIETY OF RHEUMATOLOGY
Authors: A. Damiani, G. Sakellariou, A. Adinolfi, C. A. Scirè, G. Pacini, E. Fiorentini, D. Carboni, S. Sirotti, P. Sarzi-Puttini, J. Madruga Dias, A. Iagnocco, G. Filippou
Journal: Annals of the Rheumatic Diseases (2022)

Background Musculoskeletal ultrasonography (MSUS) is a useful tool for the diagnosis of several Rheumatic and Musculoskeletal Diseases (RMDs) but its role in the diagnostic pathways in clinical practice is still unclear as feasibility issues limit its application as a bed side technique. Objectives To optimize the use of US in clinical practice, the MSUS Study Group of the Italian Society for Rheumatology aimed to develop an algorithm combining US with clinical and laboratory findings to improve the differential diagnosis among patients presenting with joint swelling. Methods Based on a systematic literature review 1 and experts’ opinion, MSUS Study Group Members attempt to identify a set of statements including the main US elementary lesions useful for US scanning in the suspicion of Rheumatoid arthritis (RA), Psoriatic arthritis (PsA), Rheumatic Polymyalgia (PMR), Gout, Calcium Pyrophosphate Deposition Disease (CPPD), Osteoarthritis (OA). Then, the MSUS Study Group defined through a survey and ranked in a 1000minds exercise the most important clinical/laboratory findings for the differential diagnosis of those diseases. Higher-ranked items were fitted in an algorithm driving the differential diagnosis of RMDs to a reduced spectrum of 2 to 4 possible diseases. Finally, the algorithm supported the performance of US according to the established scans for those specific diseases. To assess the algorithm’s performance, a pilot study was conducted on 59 patients, comparing the algorithm-based diagnosis with the final diagnosis based on rheumatologist’s experience and/or on classification criteria. Results Sets of elementary US lesions and a scanning protocol for each included pathology were created (Table 1), optimized towards high sensibility and specificity. Among the findings evaluated, the age (&lt;50 / ≥50 years old), the number of the involved joints (monoarticular/polyarticular), the serology (Rheumatoid Factor [RF] and anti-citrullinated protein antibody [ACPA]); the acute-phase reactants (C-reactive protein [CRP]; erythrocyte sedimentation rate [ESR]) reached the higher ranking in the survey and were introduced in the algorithm, showed in Figure 1. In the pilot study, the algorithm-based diagnosis was consistent with the final diagnosis in 52 cases (accuracy 88.1%). Among the 7 cases in which the algorithm misclassified patients, four patients had a final diagnosis of OA (3 diagnosed by the algorithm as PMR/RA/PSA and one as PSA), one gout (algorithm diagnosis: OA/CPPD/PSA), one RA (algorithm diagnosis: Gout/CPPD/PSA) and one CPPD (algorithm diagnosis: PMR/RA/PSA). Table 1. Elementary ultrasound lesions and joints to be scanned for each included pathology Disease Sites to scan US elementary lesions RA II-IV MCPs Synovial Hypertrophy (SH), Power Doppler (PD), erosions Wrist V MTP PsA II-III MCPs Peritendonitis PIPs Enthesitis Soft tissue oedema Flexor tendons of the hands Tenosynovitis Soft tissue oedema Achille’s tendon enthesis PD, erosions Proximal patellar tendon enthesis CPPD Knees (menisci and Hyaline Cartilage) CPP deposits Wrist (triangular fibrocartilage complex) Any involved sites CPP deposits, SH, PD Gout Knees Double contour, tophi I MTP Involved sites SH PD OA Involved sites Osteophytes Cartilage changes PMR Shoulders Bursitis Arthritis Rotator cuff integrity Figure 1. The final algorithm Conclusion The diagnostic algorithm produced in this pilot study correctly classified patients with the most prevalent RMDs in clinical practice. A longitudinal study on a large sample size is ongoing to evaluate the added value of US when implemented in this algorithm regarding diagnostic certainty, accuracy and early diagnosis. References [1]Sakellariou G, Scirè CA, Adinolfi A, Batticciotto A, Bortoluzzi A, Delle Sedie A, et al. Differential Diagnosis of Inflammatory Arthropathies by Musculoskeletal Ultrasonography: A Systematic Literature Review. Front Med. 7 maggio 2020;7:141. Disclosure of Interests None declared